This invention relates to a programmable switch for use in several application domains, such as signal processing and musical instruments having electronic pickups, for example electromagnetic, piezoelectric, or microphonic. Specifically, the embodiments disclose a programmable switch that can produce a wide range of circuit topologies with a minimum number of controls.
Signal processing applications frequently make use of filters built from combinations of circuit elements such as capacitors, resistors, and inductors. Different circuit topologies and different values of capacitance, resistance, and inductance tune the filters to different frequency ranges, and so it is valuable to have a switch that can select different circuit elements and then configure those selected elements in different ways, thereby dynamically producing different filters.
Similarly, a musical instrument that has an electronic pickup system produces dramatically different sounds depending on the pickup topology of the musical instrument. For example, in an electric guitar, a pickup topology is the use of the pickups in series, in parallel, in phase or out of phase, and different combinations of pickups, depending on the number of pickups in the guitar.
A design in the prior art that is used to achieve multiple circuit topologies, for example multiple pickup topologies on the same guitar, is a ganged, multi-pole switch. Ganged switches behave like multiple independent switches tied together. For example, two switches are illustrated in FIG. 1: a DPDT (dual-pole, dual-throw) switch 2 and a 4P5T (four-pole, five-throw) switch 4. In DPDT 2 the view of the switch is shown in 3-dimensions, and then from beneath: the switch itself is the solid rectangle, 3-dimensional view, with six leads exiting the bottom. FIG. 1 shows that dual-throw switches are normally illustrated with common leads in the center position, and switches with a larger number of settings are illustrated with common leads at the end. The two settings of the DPDT switch are shown in 6 and 8, with electrical connections between leads indicated by thick lines. The first two settings of the 4P5T switch are shown consecutively, 10 and 12, and the fifth setting, 14. The number of throws is equal to the number of switch settings; the number of poles represents the number of independent switches that are ganged together. Ganged, multi-pole switches are used in some embodiments of the disclosed invention. The notation of switches 2 and 4 is used herein.
A prior art example of the ganged switches used to switch between different circuit topologies is illustrated in FIG. 2(a). The “on-on-on” variant of the DPDT switch, which has not two but three settings, illustrated in 16, 18, and 20, can provide combinations of series, parallel, and single-element selections, given two circuit elements as input. Note that, by themselves, ganged/multipole switches provide “hardwired,” non-programmable selections of circuit topologies.
Flexibility and configurability are valuable characteristics in switch design. As an example application area, the history of development in the electric guitar industry demonstrates how such a switch would be beneficial. In a prior art guitar pickup topologies, Gibson electric guitars are known, to one of ordinary skill in the art, for the “thick” sound of the electric guitar. Gibson produces this sound by wiring the pickups in series. In another well-known guitar, the Fender Stratocaster, its sound is bright with bell-like harmonics, which are produced by wiring the pickups in parallel, or the guitarist can switch to a single pickup, via a switch on the surface of the guitar. The Fender Stratocaster then produces a clear and “clean” sound. In addition to series and parallel pickup-circuit topologies, guitarists have experimented with various custom-wired out-of-phase topologies. Guitarist Jimmy Page used a custom wiring of his Gibson Les Paul that provided more than twenty different circuit topologies using five switches, offering combinations of series, parallel, single pickup, and out-of-phase wiring.
As the number of pickups on the surface of the guitar grew, the range of possible pickups topologies grew. Guitarists also desired a reduction in the number of switches needed to obtain those different circuit topologies. Electra guitars, which were designed by St. Louis Music and built by Matsumoku in Japan in the 1970s and 1980s, offered five different circuit topologies of pickups in parallel, in series, and out of phase, using a single 5-way rotary switch. Paul Reed Smith has manufactured guitars since the 1980s that are similar to Electra's design, offering five different series/parallel circuit combinations using a 5-way rotary switch.
Manufacturers sought to provide musicians with a wider range of sounds to choose from while using a small number of performance-time controls and without changing the number of electronic pickups on the instrument, such as an electric guitar.
What is needed in the electric guitar industry is a simple programming apparatus that allows a musician to obtain as many pickup topologies as possible, using a minimum number of controls. Similarly, what is needed in the signal processing industry is a simple apparatus that allows a user to obtain multiple filter-circuit topologies and thereby to produce multiple filter characteristics such different frequency ranges, resonant frequencies, and filter types. Thus, depending on the number of switches, the present invention provides:
(a) a simple design for a single n-way control switch and a memory apparatus that allows the user to program the switch to produce any n circuit topologies out of a larger, combinatorial, number of possibilities; or
(b) given two control switches, a simple design for an apparatus that enables the user to produce all possible combinations of series/parallel/phase and circuit topologies available.